Ben Wyatt may not become a regular character on Parks and Rec until season three (with a couple of appearances at the end of season two), but he quickly became one of the most important. His love story with Leslie is absolutely heartwarming, and fans adored seeing them go from enemies (at least, work enemies) to the perfect team.
Ben also had amazing storylines with his career, his friendships, and his brilliant (if wildly complicated) game, the Cones of Dunshire. He's the resident nerd of the gang, and a total favorite - but sometimes, he absolutely breaks fans' hearts.
His Town Hating Him
Ben did something incredible as a teen - managed to actually successfully run for mayor. It's no mean feat, and no real surprise that he crashed and burned in the position. However, his town absolutely eviscerated him for those mistakes (instead of perhaps wondering if electing a teen was a smart move in the first place). It totally destroyed his self esteem, and later in life, they even called him back to 'prank' him with a fake award, just to be mean.
Treat Yo Self
One of the most beloved episodes of the show is when Donna and Tom reveal their 'treat yo self' day, where they go out and splurge on anything they want... and decide to take Ben with them, because he is miserable.
He doesn't really vibe with treat yo self to begin with, and then when he does end up treating himself to a Batman costume, he breaks down and sobs in it, broken hearted about his situation with Leslie.
Having To Play Bad Cop
When Ben and Chris first show up, it's as auditors, and they play good cop/bad cop intentionally, with Chris being the uber-positive one, and Ben coming in to be the bad guy. It works really well for them, but it's a shame that everywhere they go, the people that they work with end up hating poor Ben - when he's just playing up to a dynamic!
The Breakup With Leslie
Ben and Leslie didn't have a smooth relationship, as their romance threatened Leslie's career. They decided that her run for office was more important, and agreed to split - and he even gave her a 'Knope 2012' button. It was touching and lovely, but absolutely heartbreaking for both of them.
Being Looked Down On For His Nerdiness
One of Ben's defining traits is his love of nerd culture. He is a huge fan of Game of Thrones, Lord of the Rings, and all things geek - which is actually pretty mainstream! However, the rest of the gang tend to make fun of him for being a 'nerd', and make jokes about the things that he loves, which is just not cool.
Having Andy & April As Roommates
Ben moves in with Andy and April after he decides to stay in Pawnee, but it's far from an easy living situation. Andy and April are adorable, but utterly incapable of being functional adults, so Ben has to step in and become something of a parental figure for them.
He also has to deal with all the various terrible roommate things that they do, including getting a dog without discussing it, having a big Halloween party and not telling him, and using all his stuff without asking.
How Tom Treats Him
While most of the gang tends to look down on Ben a little, Tom takes it to another level. Even when Ben helps him out with his businesses, Tom acts as though he is the one doing Ben a favor! He constantly calls him boring, dull, nerdy, and all kinds of names, and tries to push Donna into not including him in treat yo self.
Losing His Job For His Relationship
After Leslie and Ben decide that they have to be together, it causes some serious issues for everyone - their relationship is considered unethical, and Leslie could lose her job over it. Instead, Ben takes the hit. He resigns, so that she can be let off with a suspension. It's an amazing thing for him to do for Leslie, but it's also pretty sad that he had to lose his own job to save hers.
Giving Up His Bachelor Party
When Ben and Leslie were planning their wedding, all Ben wanted for his bachelor party was a low key night in, playing a board game with his friends. It was a night that suited Ben perfectly, but he ended up creating a night where everyone got a couple of hours for their perfect party. Again, an incredibly sweet gesture, but it's a shame Ben couldn't just have one night for himself.
His Low Self Esteem
A lot of these sad moments all come from the same root - that Ben has chronically low self esteem. Between Ice Town and being bullied for being nerdy, Ben clearly feels like he's just not good enough, and it shows in everything he does. He finds it hard to take compliments, he lets people walk all over him, he accepts insults as just par for the course. It's absolutely heartbreaking, especially as Ben is such a great person.